[PATCH 3/9] USB: add devicetree helpers for determining dr_mode and phy_type

[Felipe Balbi]

Hi,

On Thu, Feb 14, 2013 at 10:49:44AM +0100, Marc Kleine-Budde wrote:
> >> diff --git a/drivers/usb/usb-common.c b/drivers/usb/usb-common.c
> >> index d29503e..ad4d87d 100644
> >> --- a/drivers/usb/usb-common.c
> >> +++ b/drivers/usb/usb-common.c
> >> @@ -14,6 +14,9 @@
> >>  #include <linux/kernel.h>
> >>  #include <linux/module.h>
> >>  #include <linux/usb/ch9.h>
> >> +#include <linux/of.h>
> >> +#include <linux/usb/of.h>
> >> +#include <linux/usb/otg.h>
> >>  
> >>  const char *usb_speed_string(enum usb_device_speed speed)
> >>  {
> >> @@ -32,4 +35,37 @@ const char *usb_speed_string(enum usb_device_speed speed)
> >>  }
> >>  EXPORT_SYMBOL_GPL(usb_speed_string);
> >>  
> >> +#ifdef CONFIG_OF
> >> +static const char *usb_dr_modes[] = {
> >> +	[USB_DR_MODE_UNKNOWN]		= "",
> >> +	[USB_DR_MODE_HOST]		= "host",
> >> +	[USB_DR_MODE_PERIPHERAL]	= "peripheral",
> >> +	[USB_DR_MODE_OTG]		= "otg",
> >> +};
> > 
> > It turns out this is a problem, especially since this is generic usb
> > code: we have a chipidea controller (a patchset just arrived) that does
> > both host and peripheral, but not otg. And I'm told now that dwc3
> > controller can be synthesized like that too.

I wonder if this part is really necessary. Usually you would read it
from HW's registers. For dwc3, it's quite recently that we allowed the
driver to be built with host-only, device-only or DRD functionality.

Also, this is likely to create troubles if not done correctly. Imagine
user compiles a host-only driver and board passes dr_mode = peripheral ?

Maybe we can ignore dr_mode in host-only and device-only builds and only
look at it for DRD builds ?

> You mean a single instance of the controller (i.e. USB port) is host and
> peripheral but has no otg registers. This means the mode of the port is
> configured by userspace via the debugfs file? Is this possible?

yes, it is possible. Dual-Role doesn't imply OTG, but OTG implies
Dual-Role.

> The above property describes a single port not the whole controller. If
> there is a controller with one host and one peripheral port the code in
> this patch should be sufficient, as you have a property in the DT for
> each port.

I don't think you can have a single controller like that, but good that
it supports.

-- 
balbi
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